1. Field of the Invention
The present invention relates to an automatic sliced piece fabricating apparatus for automatically fabricating a sliced piece used in a scientific experiment or microscopic observation and an automatic sliced piece sample fabricating apparatus for automatically fabricating a sliced piece sample by fixing a fabricated sliced piece on a base plate.
2. Description of the Related Art
In a related art, there is carried out a toxic test or a pathological inspection on an experimental animal prior to a clinical test in developing a new drug. The test or the inspection is carried out by using a sliced piece sample fixed with a sliced piece having a thickness of several μm, (for example, 3 μm through 5 μm) on a base plate of a slide glass or the like. There is used a sliced piece sliced for a pathological inspection by subjecting an experimental animal of a mouse or a rabbit administered with a drug to autopsy. Further, sliced pieces are fabricated for respective various portions (for example, brain or lung or the like).
A microtome is known as an apparatus for fabricating such a sliced piece sample. Here, an explanation will be given of a general method of fabricating a sliced piece sample by utilizing a microtome.
First, an enveloped block in a block state is fabricated by subjecting a living body sample of a living thing, such as an animal or the like, fixed by formalin to paraffin substitution, and thereafter, further hardening a surrounding thereof by paraffin to be solid. Next, rough machining is carried out by setting the enveloped block to a microtome constituting an exclusive slicing apparatus. By the rough machining, a surface of the enveloped block becomes a smooth face and there is brought about a state of exposing the enveloped living body sample constituting an object of experiment or observation at the surface.
After finishing the rough machining, regular machining is carried out. This is a step of slicing the enveloped block to be extremely thin by the above-described thickness by a cutting blade provided to the microtome. Thereby, the sliced piece can be provided. At this occasion, by slicing the enveloped block as thin as possible, the thickness of the sliced piece can be made to be proximate to a thickness of cell level and therefore, further accurate observation data can be provided. Therefore, it is requested to fabricate the sliced piece having a thickness as thin as possible. Further, the regular cutting is continuously carried out until providing a necessary number of sheets of the sliced pieces.
Next, there is carried out an elongating step for elongating the sliced piece provided by the regular machining. That is, the sliced piece fabricated by the regular machining is brought into a wrinkled state or a rounded state (for example, U-like shape) since the sliced piece is sliced to the extremely thin thickness as described above. Hence, it is necessary to elongate the sliced piece by removing wrinkle or roundness by the elongating step.
Generally, the sliced piece is elongated by utilizing water and hot water. First, the sliced piece provided by the regular machining is floated on water. Thereby, large wrinkle or roundness of the sliced piece can be removed while preventing portions of paraffin enveloping the living body sample from being stuck. Thereafter, the sliced piece is floated on hot water. Thereby, the sliced piece is easy to be elongated and therefore, remaining wrinkle or roundness which cannot be removed by being elongated by water can be removed.
Further, the sliced piece finished with the elongation by hot water is scooped by a base plate of slide glass or the like to be mounted on the base plate. Further, when the elongation is insufficient assumedly at the time point, the sliced piece is mounted on a hot plate or the like along with the base plate and is heated further. Thereby, the sliced piece can further be elongated.
Finally, the base plate mounted with the sliced piece is put into a dehydrator to be dried. By the drying, moisture adhered by the elongation is evaporated and the sliced piece is fixed onto the base plate. As a result, the sliced piece sample can be fabricated.
Here, although paraffin used as the enveloped block having a melting point of a temperature as low as possible is preferable to prevent a living body tissue from being denatured, on the other hand, it is preferable that the melting point is as high as possible in order to prevent softening under a temperature of a slicing operational environment. Hence, paraffin having a melting point of about 60° C. is used in reality by compromising both requirements.
However, even when such paraffin is used, the temperature of the operational environment constitutes a limit by 20° C. corresponding to a temperature of starting to soften paraffin at the lowest temperature and therefore, there is a concern of gradually softening paraffin with an elapse of time. When paraffin is assumedly softened, slicing becomes difficult, a sliced piece cut out from an enveloped block is broken or easy to be deformed. Hence, in order to prevent such a drawback as less as possible, generally, an enveloped block is previously cooled by a refrigerator or iced water or the like. Further, a sliced piece is cut out by setting the cooled enveloped block to a microtome immediately before being cut.
However, even when the above-described method is adopted, although a problem is not posed at start, the temperature of the enveloped block rises with time and therefore, the enveloped block is elongated, and hardness or friction coefficient of paraffin is gradually changed. That is, cutting cannot be carried out always under the same condition. Therefore, in fabricating the sliced piece, fine adjustment of a cutting amount of the microtome, or adjustment of temporarily cooling a surface of the enveloped block by ice is obliged to be carried out auxiliarily by empirically determining a thickness or a shape from the sliced piece cut out by an operator.
Hence, in order to resolve such a drawback as less as possible, there is proposed an apparatus of integrating a Pertier element at a portion of holding an enveloped block and cooling a bottom face of the enveloped block by the Pertier element (for example, JP-A-2004-317515). According to the apparatus, the sliced piece can be cut out in a state of restraining a temperature rise of the previously cooled enveloped block as low as possible.
However, according to the related art apparatus, the following problem still remains.
That is, according to the apparatus, the bottom face of the enveloped block is cooled by the Pertier element and therefore, it is difficult to control a temperature at a vicinity of a surface of the enveloped block (for example, a range of several μm from the surface). That is, since the thermal conduction coefficient of paraffin is small, even when the bottom face is cooled, it is difficult to control a surface temperature related to cutting. Thereby, in fabricating the sliced piece, heat generated by a friction with a cutting blade cannot be absorbed and a good quality sliced piece cannot uniformly be fabricated by the influence of the heat. That is, the hardness or the friction coefficient of paraffin is changed by the heat and the sliced piece is liable to be deformed or broken. Therefore, the auxiliary adjustment based on hunch or experience is obliged to be carried out manually. Particularly, the fact constitutes a factor of remarkably hampering automation of the sliced piece.